David Marjanovic <david.marjanovic@gmx.at> wrote:
> David Burnham (2 February 2010): Maniraptoran "Dinosaurs":
> Paleoenvironment, Paleoecology, and Evolution. VDM ( =
> Verlag Dr. Müller). Paperback, 128 pp.
>
> Yes, scare quotes in the title. Yes, a German publisher.
And yes, we've seen it all before. The gist of the book was presaged in a
paper from a few years ago:
http://dml.cmnh.org/2007Nov/msg00381.htmlhttp://dml.cmnh.org/2007Nov/msg00401.html
> Maniraptora includes the first known bird, Archaeopteryx,
> the small, four-winged, feathered glider, Microraptor, and
> the terrestrial runner Bambiraptor.
There is no justifiable reason for interpreting _Microraptor_ and _Bambiraptor_
as having highly contrasting lifestyles. They both have essentially the same
morphology - so why is one regarded as a "feathered glider" and the other as a
"terrestrial runner"? Osteologically, there is very little difference between
the two. It's only because _Microraptor_ specimens come preserved with
integument that we can infer that this little dromaeosaurid was likely capable
of aerial behavior. But there is no preserved integument for _Bambiraptor_, so
it remains an open question whether it was a glider or not.
In fact, according to Senter's work, _Bambiraptor_ is the only theropod to have
a prehensile manus. This is a trait that might actually be considered
appropriate for a tree-climbing animal...
> The discovery of a gliding stage within the
> dromaeosaurs confounds the currently suggested evolutionary
> framework and lacks predictability for origin of flight
> scenarios.
Well, this is just plain nonsense. Again the author is deliberately conflating
the origin of birds (a phylogenetic issue) with the origin of flight (an
ecomorphological issue). Sure, the two are intimately interwoven; but they are
not one and the same. Phylogeny tells us the most parsimonious pathway by
which characters were gained (or lost). The ecomorphological hypothesis on the
origin of flight has to be consistent with this pathway.
A theropod origin of birds does *not* equal a "ground-up" origin of flight.
Phylogeny seems to be telling us that certain flight-related characters (i.e.,
characters that form part of the flight apparatus) evolved on the ground,
whereas others evolved specifically for aerial locomotion. So to answer the
question "Was the origin of avian flight ground-up or trees-down?" I would
reply, "Yes!". It was both.
Cheers
Tim